Is tinning stripboard traces useful?

Discussion in 'The Projects Forum' started by dentaku, Sep 9, 2014.

  1. dentaku

    Thread Starter Member

    Jul 29, 2013
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    I decided to finally build something on stripboard.
    It's a roughly -/+ 20V power supply with an LM317 and 337.

    I've seen old circuit boards with extra thick tinned traces and modern ones with wider traces leading to higher power devices.

    Is it a good idea to tin the traces leading to the input and output of the voltage regulators to fill in the holes along the trace. It seems to me that the edges of the holes are quite a bottleneck.

    I see LM317/337 regulators aren't rated for more than 1.5A but since it doesn't seem terribly difficult to lay some extra solder on the traces it might be a good thing to do.

    If it IS a good idea, is there anywhere else worth doing this to other that the traces between the bridge rectifier and input and between the outputs to the binding posts?
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    For those regulators and maximum current derived, the average strip board is sufficient IMO.
    If you want to increase the area for some reason, just use two adjacent strips.
    Max.
     
    dentaku likes this.
  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    but yes.. some people commonly fill in the holes to attempt to increase current capacity.
    Nothing "wrong" with it.. but there are other reasons as suggested by Max.
     
  4. crutschow

    Expert

    Mar 14, 2008
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    3,237
    The edges of the holes provide no bottleneck, it's just the reduced trace area caused by the holes that increases resistance.

    In most cases the trace resistance is unlikely to be a problem in your circuit except possibly the trace from the LM317 output to the output terminal. The LM317 can't compensate for that resistance voltage drop due to the output current so you can make it lower by adding thick solder or using two or more traces.
     
  5. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    It is more of personal preference then necessity. By tinning the strip you make it easier to solder to, but you also increase the chance of lifting the land itself.

    If I wanted the land to carry a heavy current I would solder a solid bus wire on top of it.
     
  6. MrAl

    Well-Known Member

    Jun 17, 2014
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    Hi,

    The resistance of solder is quite a bit higher than copper, on the order of 5 to 10 times higher. That means if you want to double the current rating of a strip of copper on a copper clad board, you need a layer of solder that is at least 5 times as thick as the copper trace. This is not easy to get, and there are drawbacks.

    One drawback is as the solder cools it has a tendency to warp the board. This may not be too bad in some cases but might be worse in others.
    Another drawback is it takes a lot of solder for a lot of traces.
    Another drawback is there's a lot of flux cleanup afterward.
    One good point is if the board is not tin plated (a lot of hobby boards) then a thin layer of solder protects it from ugly deterioration over time. Unprotected copper can get really ugly green in the presence of moisture.

    As mentioned elsewhere in this thread (Ernie), a heavy copper wire soldered to several key points along the trace works much better. It's not too nice looking but it works great, and if this is thought about during the board planning you can actually use heavy jumpers instead of just traces and that way leave some insulation on too to make a nice neat pro looking job.
     
  7. dentaku

    Thread Starter Member

    Jul 29, 2013
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    2
    I ended up just shifting the position of one wire so it's directly next to the output pin of one regulator and the other uses a solid copper wire jumper with the wire that leads to the binding post soldered in the hole next to it.
    I tinned another trace but I don't remember what it's connected to now it's in the enclosure.
    So far it seems to work.
     
  8. MrAl

    Well-Known Member

    Jun 17, 2014
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    Hi,

    Oh that sounds good, happy to hear it worked out for you. Redesigning the board is always the best way.

    I also forgot to mention that the thermal conductivity of solder is not as good as copper either, so there is another diminishing return there because the solder does not conduct the heat away from the entire trace to the surface as well, and also there's the volume to surface area rule that shows that the surface area to width ratio is not as good as a flat trace either, so we have another fault that limits the current with added material volume.
    It's a wonder it works at all, and if there is a limit point where it actually makes the trace heat up MORE than it did without the solder.
     
  9. Lee697

    New Member

    Aug 31, 2014
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    +1 - I do this a bit - just run a piece of tinned copper wire over the trace....
     
  10. dentaku

    Thread Starter Member

    Jul 29, 2013
    45
    2
    Last edited: Sep 12, 2014
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